TCP%20Interactive%20Data%20Flow

1
TCP Interactive Data Flow

• miyu

2
Whats talk about?

• Transfer of data using TCP
• Interactive data bulk data
• Delayed acknowledgments
• Nagle algorithm
• Window size advertisement

3
Bulk data Interactive data

• bulk data
• ftp, electronic mail, Usenet news
• Tend to be full sized(normally 512 bytes)
• Interactive data
• telnet,rlogin
• Much smaller (90 of packets less than 10bytes)

4
Interactive Input
client
server
data byte
keystroke
server
ack for data byte
echo of data byte
echo
display
ack of echoed byte
5
Flow of data typed date\n

• 1 0.0 bsdi.1023 gt svr4.login P 01(1) ack 1 win
  4096
• 2 0.016497 (0.0165) svr4.login gt bsdi.1023 P
  12(1) ack 1 win 4096
• 3 0.139955 (0.1235) bsdi.1023 gt svr4.login . ack
  2 win 4096
• 4 0.458037 (0.3181) bsdi.1023 gt svr4.login P
  12(1) ack 2 win 4096
• 5 0.474386 (0.0163) svr4.login gt bsdi.1023 P
  23(1) ack 2 win 4096
• 6 0.539943 (0.0656) bsdi.1023 gt svr4.login . ack
  3 win 4096
• 7 0.814582 (0.2746) bsdi.1023 gt svr4.login P
  23(1) ack 3 win 4096
• 8 0.831108 (0.0165) svr4.login gt bsdi.1023 P
  34(1) ack 3 win 4096
• 9 0.940112 (0.1090) bsdi.1023 gt svr4.login . ack
  4 win 4096
• 10 1.191287 (0.2512) bsdi.1023 gt svr4.login P
  34(1) ack 4 win 4096
• 11 1.207701 (0.0164) svr4.login gt bsdi.1023 P
  45(1) ack 4 win 4096
• 12 1.339994 (0.1323) bsdi.1023 gt svr4.login .
  ack 5 win 4096
• 13 1.680646 (0.3407) bsdi.1023 gt svr4.login P
  45(1) ack 5 win 4096
• 14 1.697977 (0.0173) svr4.login gt bsdi.1023 P
  57(2) ack 5 win 4096
• 15 1.739974 (0.0420) bsdi.1023 gt svr4.login .
  ack 7 win 4096
• 16 1.799841 (0.0599) svr4.login gt bsdi.1023 P
  737(30) ack 5 win 4096
• 17 1.940176 (0.1403) bsdi.1023 gt svr4.login .
  ack 37 win 4096
• 18 1.944338 (0.0042) svr4.login gt bsdi.1023 P
  3744(7) ack 5 win 4096
• 19 2.140110 (0.1958) bsdi.1023 gt svr4.login .
  ack 44 win 4096

6
Delayed Acknowledgments
PSH 01 ack 1 (d)
1
0.0
2
PSH 12 (1) ack 1 (echo d)
0..16497(0.0165)
Delayed ack
ack 2
3
0.139955(0.1235)
4
PSH 12 (1) ack 2 (a)
0.4580378(0.3181)
PSH 12 (1)ack 2 (echo a)
5
0.47386(0.0163)
Delayed ack
6
ack 3
0.539943(0.0656)
PSH 23 (1) ack 3 (t)
0.814582(0.2746)
7
8
PSH 12 (1)ack 2 (echo a)
0.831108(0.0165)
Delayed ack
ack 4
0.940112(0.1090)
9
7
Nagle algorithm

• RFC 896
• solution of tinygrams congestion on wide area
  networks(Simple and Elegant)

8
Nagle algorithm

• Have only one outstanding small segment that has
  not yet been ackonwleged
• Small amounts of data are collected by TCP
• sent in a single segment when the acknowledgement
  arrives
• Self-clocking
• The faster the ACKs come back,the faster the data
  is sent
• On a slow WAN(desired to reduce the number of
  tinygrans),fewer segments are sent

9
When the RTT incleases
10
Disabling the Nagle algorithm

• When small message(and mouse movements) must be
  deliverd
• ex)X Windows System server
• Typing one of the terminals special function
  keys during an interactive login
• Normally generate multiple bytes of data
• Often beginning with ESC (ASCII)

11
PSH 12 (1)ack 2
type F1
PSH 23(1)ack2
PSH 34(1)ack 2
PSH 25(3)ack 3
lost
PSH 56(1)ack 4
ack 2
Timeout and retransmisson
PSH 26(4)ack 4
ack 6
PSH 45(1)ack 6
type F2
PSH 56(1)ack 6
PSH 67(1)ack 6
F2 F1
PSH 68(3)ack 5
F2echo F1echo
PSH 68(1)ack 7
ack 10
N I ESC M ESC
N ESC M ESC
M N
12
Window Size Advertisements

• Why Segment 5 advertises a window of 4095 bytes?
• Still 1 byte in the TCP buffer for the
  application to read.
• When the client TCP sends the buffered data
• Clienthad a chance to read the data from the
  server
• Clients advertised window is less the 4096

13
Summary

• Interactive data
• Nagle algorithm
• Disabling the Nagle algorithm

14
END

• Va bena?